Investigation of Product Formation in the O(1D, 3P) + N2O Reactions: Comparison of Experimental and Theoretical Kinetics

The spin-forbidden and spin-allowed reactions of the excited and ground electronic state O(D-1, P-3) + N2O(X-1 Sigma(+)) systems have been studied theoretically. Quantum calculations at the UCCSD(T)/CBS(T, Q, 5)//CCSD/aug-cc-pVTZ level have located two crossing points, MSX1 and MSX2, with energies of 11.2 and 22.7 kcal mol(-1) above O((3P)) + N2O, respectively. The second-order P-independent rate constants for the adiabatic and non-adiabatic thermal reactions predicted by adiabatic TST/VTST and non-adiabatic TST, respectively, agree closely with the available literature results. The second-order rate constant, k(2a) = 9.55 x 10(-11) exp(-26.09 kcal mol(-1)/RT) cm(3) molecule(-1) s(-1), for the O(P-3) + N2O -> 2NO reaction, contributed by both the dominant MSX2 and the minor TS1-a channels, is in reasonable accord with prior experiments and recommendations, covering the temperature range of 1200-4100 K. The calculated rate constant, k(2b) = 4.47 x 10(-12) exp(-12.9 kcal mol(-1)/RT) cm(3) molecule(-1) s(-1), for the O(P-3) + N2O -> N-2 + O-2(a(1)Delta(g)) reaction, occurring exclusively via MSX1, is also in good agreement with the combined experimental data measured in a shock tube study at T = 1940-3340 K (ref 16) and the result measured by Fourier transform infrared spectroscopy in the temperature range of 988-1083 K (ref 17). Moreover, the spin-allowed rate constants predicted for the singlet-state reactions, k(1a) = (7.06-7.46) x 10(-11) cm(3) molecule(-1) s(-1) for O(D-1) + N2O -> 2NO and k(1b) = (4.36-4.66) x 10(-11) cm3 molecule(-1) s(-1) for O(D-1) + N2O -> N2 + O-2(a(1)Delta(g)) in the temperature range of 200-350 K, agree quantitatively with the experimentally measured data, while the total rate constant k(1) = k(1a) + k(1b) was also found to be in excellent accordance with many reported values.

Automated summary

The spin-forbidden and spin-allowed reactions of the O(D-1, P-3) + N2O system were studied. The calculated rate constants for various reactions showed good agreement with experimental data and literature results.